This invention relates to a disk drive device suitable for use in a CD-ROM (Compact Disk as Read Only Memory) or the like, for example, and a method of setting a rotational speed of the disk drive device. This invention relates specifically to a disk drive device for determining or distinguishing that a disk-shaped recording medium is either an eccentric disk or an unbalance disk in a state in which the disk-shaped recording medium is being rotated at a predetermined speed. When it is determined that the disk is either the eccentric disk or the unbalance disk, a rotational speed of the disk drive device is reduced to thereby lessen the vibrations transferred to the outside and to maintain high performance against external vibrations and impact, and satisfactorily perform a recording and reproducing operations. This invention also relates to a disk drive device or the like capable of, when it is determined in a state in which a disk-shaped recording medium is being rotated at a predetermined speed, that the disk-shaped recording medium is neither an eccentric disk nor an unbalance disk, increasing its rotational speed to thereby read data at high speed.
This invention relates to a disk drive device or the like, of a type wherein when it is distinguished in a state in which a disk-shaped recording medium is being rotated at a predetermined speed, that an external vibration or impact of a predetermined level or more has occurred, its rotational speed is reduced to thereby lessen the influence of the external vibration or impact of the predetermined level or more on recording and reproducing operations.
FIG. 20 shows a principal portion of a related CD-ROM drive device. Referring to FIG. 20, a pair of pin support holes (not shown) is defined in both side plates 50a of a fixed case. A pair of pins 53 of a base unit holder 52 is inserted into their corresponding pin support holes. An elevation pin 54 is provided on side opposite to the provision of the pair of pins 53 of the base unit holder 52. The elevation pin 54 is displaced in upward and downward directions by a base unit elevation mechanism (not shown) so that the one-end side of the base unit holder 52 moves up and down. Bosses 55 are placed in three points of the base unit holder 52. Threaded holes 56 are defined in their corresponding bosses 55.
A base unit 57 has a base plate 58 to which an optical pick-up unit 59 for reproducing data from a disk, a disk rotating unit 60 having a spindle motor for rotating the disk, etc. have been attached. Mounting holes 61 are respectively provided at three points of the base plate 58. The base unit 57 is mounted to the base unit holder 52 by using mounting vises 62 with insulator 63 used as damping members composed of rubber.
FIG. 21 shows a mounting portion of the base unit 57 in a developed form. Referring to FIG. 21, the insulators 63 are mounted in their corresponding mounting holes 61 defined in the base plate 58 of the base unit 57. The mounting vises 62 inserted into the holes of the insulators 63 are threadedly inserted into threaded holes 56 of the bosses 55 of the base unit holder 52.
In the aforementioned construction, an external vibration or impact is transmitted to the base unit holder 52 through the fixed case 50 without attenuation so far. The vibration transmitted to the base unit holder 52 is transmitted to the base unit 57 through the insulators 63 for providing damping action. Thus, the external vibration and impact is attenuated and applied to the base unit 57, so that the adverse effects of the vibration and impact thereon is lessened.
An external vibration characteristic of the base unit 57 has a resonance point at a range of 100 Hz to 120 Hz, for example, as shown in FIG. 22.
Further, the number of revolutions of the disk ranges from 200 rpm to 500 rpm (3.3 to 8.3 Hz) at a standard speed, ranges from 800 rpm to 2000 rpm (13 to 33 Hz) at a quadruple speed, ranges from 1200 rpm to 3000 rpm (20 to 50 Hz) at a sextuple speed, ranges from 1600 rpm to 4000 rpm (27 to 67 Hz) at an octuple speed, and ranges from 2400 rpm to 6000 rpm (40 to 100 Hz) at a dodecuple speed.
When the disk is an unbalance disk and is rotated at a high speed of about 3000 rpm, a self-induced vibration having a frequency corresponding to the number of revolutions of the disk occurs. There is a problem in that this self-induced vibration is transmitted to the outside of the drive device through the base unit 57 and the insulators 63, thus giving an unpleasant feeling to a user. Further, a problem arises in that tracking control of the optical pick-up unit 59 falls into difficulties due to this self-induced vibration, so that data cannot be reproduced from the disk.
FIG. 23 shows a transmission characteristic of each insulator 63. When the insulator 63 is formed of butyl rubber, a resonance point f0 of the insulator 63 can be set to a range of 25 to 130 Hz. As the resonance f0 is made greater, a Q value is reduced so that an attenuatable frequency is shifted to a high frequency.
It is desirable that the resonance point of the insulator 63 is set so as to attenuate 100 to 120 Hz corresponding to the resonance point of the vibration characteristic of the base unit 57 and escape from a frequency corresponding to the number of revolutions of the disk, which is to be used. However, since the number of revolutions to be used increases as in the case of the sextuple speed, octuple speed, . . . , it is difficult to satisfy the two.
Therefore, for example, the resonance point f0 of the insulator 63 was set so as to be higher than the maximum number of revolutions of the disk and to satisfy escaping from the frequency corresponding to the number of revolutions of the disk, which is to be used. Therefore, although the problem about the aforementioned self-induced vibration can be lessened, the range of 100 to 120 Hz corresponding to the resonance point of the vibration characteristic of the base unit 57 cannot be attenuated sufficiently, thus resulting in significant reduction in the performance against an external vibration and impact.
When the number of revolutions of the disk increases, the influence of the external vibration or impact on the tracking control or the like becomes strong in general. Thus, when the vibration and impact of the predetermined level or more occur, it is considered that the number of rotations of the disk is reduced and the influence of the vibration and impact on the reproduction of data from the disk is lessened.
Therefore, an object of the present invention is to lessen vibrations transferred to the outside, maintain high performance against an external vibration and impact, and satisfactorily perform recording and reproducing operations. Another object of the present invention is to lessen the influence of an external vibration or impact of a predetermined level or more on recording and reproducing operations.